Grapes, banana, juice, and yes: Elements of İanguage in non-human primates Reyhan Furman Boğaziçi University, Koç University Bu makale insan olmayan primatlardaki dil öğelerini araştıran çalışmaları özetlemektedir. Kitap ve makaleler beş ana başlık altında toplanmıştır: sembol kullanma ve gönderi becerileri, dil anlama, dil üretimi ve türe özgü bir yetenek olarak dil. Alanda yapılmış çalışmaların incelenmesinin ardından bu çalışmalara yöneltilen eleştiriler ve eleştirilere verilen cevaplar kısaca özetlenmiştir. Dil yeteneklerinin sadece insanlara özgü olmadığı ve temellerinin değişik hayvan türlerinde bulunduğu sonucuna varılmıştır. Primatların dil becerilerinin çocuklarınkine benzediği, fakat dilbilgisi gelişiminin primatlarda çocuklara kıyasla daha yavaş ve kısıtlı olduğu bulunmuştur. Ek olarak, primatların dil anlama ve üretme becerileri iki yaşındaki çocuklarınkinden ileri gidememektedir. Primatlardaki dil öğelerini araştıran çalışmalar içerdikleri çeşitli sınırlama ve eksiklere rağmen dilin edinimi, gelişimi, ve çevreyle olan ilişkisini irdeleyebilmek için önemli modeller sunmaktadır. Introduction For years researchers have tried to teach primates İanguage. Although seemingly very successful at fırst, early investigations of primates’ linguistic abilities have generated much controversy and, in a way, disappointment. As syntax was thought to be the most unique component of human İanguage, research naturally focused on the complexity of apes’ symbolic utterances. Yet, vvhen analyzed deeply, in many cases the apes’ utterances turned out to be the repetitions of those of the researchers’. The consequent research on primates abandoned syntax and explored the referential ski 1 İs, İanguage comprehension and İanguage production. Studies on the referential ski 1 İs and symbol use of apes provided evidence that apes did have true referential skills and that they could use symbols vvhen communicating vvith each other. The symbol processing of apes resembled that of humans, particularly that of chimpanzees exhibited both hemispheric specialization and long-term memory for symbols. Language comprehension studies revealed that bonobos could uııderstand speech as vvell as tvvo-year-old children. Also, to an extent, comprehension skills proved to be species specifıc. The İanguage production of apes vvas stili another important topic investigated över the recent years. Researchers found that the symbolic utterances of bonobos had proto-grammatical 100 Dilbilim Araştırmaları 2003 rııles and that their language system contained elements of syntax. İn the follovving sections, each of the main investigation topics is reviewed, It has to be emphasized that this review does not inquire whether non-human primates have language but vvhich elements of language they might have. Referentiaf sküls and svınbol use One of the earliest studies on referential skills and symbol use bv apes vvas conducted in the early 1970s. The sign-language-trained chimpanzees, participating in the studies, could combine symbols in the sentences to request objects or activities but they failed to recognize the same symbols when a human made a request. Soon it became apparent that they did not possess ful 1 linguistic referential abilities and unless they learned to use symbols referentially, their potential for having language capacities could not be studied (Savage-Rumbaugh & Lewin, 1994). Accordingly, the studies that followed focused rather on symbols (vvords) than syntax (sentences) and the ability of chimpanzees to use symbols referentially vvith each other in a vvav that reseınbled human communication. The referential skills of apes were studied in detail on two male chimpanzees (Sherman and Austin). The chimpanzees received structured, reward-based training and iearned lexigrams that were arbitrary geometric symbols. The lexigrams could be produced as visual dispiays by pressing keys on a Computer keyboard. Through extensive training, Sherman and Austin were able to use about 100 lexigrams that symbolized foods, locations, people, tools, and other objects. Similarly, after being taught each step in many trials, they deveioped communicative skills (Savage- Rumbaugh, 1986, as cited in Cranfield, 1995). Their symbol production skills, hovvever, did not generalize to symbol comprehension. Furthermore, their symbol comprehension never led to comprehension of human speech. Stili, despite ali these jimitations, Sherman and Austin demonstrated unexpected components of communication that resembled basic human communication. ‘Once these [the keys elements of communication- requesting. narning and comprehension- were in place, the other aspects of communication emerged spontaneously. The chimps began to pay close attention to each other’s Communications; they engaged each other before delivering their message; they gestured to emphasize or clarify messages; they took turns. None of these behaviors, ali of vvhich enhance communication, was taught by us. Sherman and Austin deveioped them spontaneously’ (Savage-Rumbaugh & Lewin, 1994). Most importantly, the apes spontaneously displayed the ability to announce their future actions. As typical examples, one can çite Austin pressing the funny face lexigram and making it or Sherman announcing Go sink and vvalking to the kitchen vvhere he played at the counter (Savage-Rumbaugh, 1986, cited in Cranfield, 1995). The work vvith Austin and Sherman proved that apes are not only capable of using symbols referentially but they can also use symbols to Reyhan Furman 101 communicate with their conspecifics (Savage-Rumbaugh et al., 1993). Hemispheric specialization in İanguage functions has been hypothesized to be unique to humans. To test this, Hopkins et al. (1992) examined hemispheric asymmetries of language-trained chimpanzees by using a vvarning stimulus, which specifıcally activated each hemisphere. The warning stimulus could be a meaningful (food or tool lexigrams) or a nonmeaningfiıl (familiar lexigrams with no associated meaning) symbol. Priming of the left hemisphere occurred only by meaningful symbols. Thus, the results indicate that hemispheric asymmetries for processing communicative symbols exist in language-trained chimpanzees and the chimpanzees’ perception of meaningful symbols is similar to humans’ perception of words. The fındings of Hopkins el al. are consistent with the study that has shown that Broca’s area in the brain of the great apes (chimpanzees, bonobos and gorillas) is larger in the left hemisphere (Cantalupo & Hopkins, 2001). Linked to the İanguage and speech, this asymmetry was previously thought to be unique to humans and taking into consideration the primitive vocalization skills of the apes’, it is a rather unexpected fınding. On the other hand, Broca’s area might have been specialized for gestural communication long before it evolved to play a crucial role in human speech. Manual gestures of untrained chimpanzees also showed a left hemisphere bias (Hopkins & Leavens, 1998). The gestures were both intentional and referential, and were done predominantly by the right hand, vvhich was controlled by the left hemisphere. The right-hand preference became more prominent vvhen the chimpanzees simultaneously vocalized and gestured. These results suggest that communicative behaviors are lateralized to the left hemisphere in chimpanzees. Beran et al. (2000) investigated whether a language-trained chimpanzee could have a long-term memory for symbols similar to humans. They examined the long- term retention of lexigrams of a female language-trained chimpanzee (Lana). Lana was presented vvith various objects, foods and colors, and asked to label them by choosing the correct lexigram. After not having encountered some lexigrams for 20 years, she was stili able to recognize them consistently. Lana’s long-term memory vvas similar to humans’ ability to remember information for variable lengths of time. Language comprehension Language-trained chimpanzees seem to resemble humans in the vvay they use and process symbols. Yet, there is a crucial difference between them: the chimpanzees require extensive training to acquire linguistic abilities whereas humans do not have to be trained to learn İanguage. This point was challenged by the later studies vvith a male bonobo (Kanzi). Kanzi vvas indirectly exposed to lexigrams and spoken İanguage in infancy vvhen Savage-Rumbaugh and her colleagues vvere trying unsuccessfully to train his mother. After being separated 102 Dilbilim Araştırmaları 2003 from his mother, Kanzi started to use lexigrams spontaneously and it became apparent that he had learned to use lexigrams through observation. Aftervvards, his language-learning environment involved participation in daily laboratorv activities with researchers. Whenever the researchers talked to Kanzi, they also shovved him the lexigrams that corresponded to the words they used. Although he vvas not required to produce lexigrams in return for food or other revvards, he watehed as others utilized the lexigram board. Interactions with Kanzi revealed that his ability to comprehend speech was related to his lexigram use. Similar to human children, his comprehension of new lexigrams or spoken vvords preceded his lexigram production (Savage-Rumbaugh et al., 1993). His speech comprehension skills were examined in comparison to a tvvo- year-old female chiId's in an experiment. Kanzi and the child (Alia) vvere independently exposed to sentences that vvere uttered by an experimenter hidden behind a one-way mirror and had to carry out the requests